Considerable experimentation and development in water culture or hydroponic culture has brought the art to where some plants, particularly adaptable to hydroponic culture, are commercially hydroponically cultured to a limited extent, and it is expected that significant portions of certain plants might soon be hydroponically grown. A major advantage of hydroponic culture, is that through the use of efficient systems, the yield per unit space can be substantially greater than that achievable with conventional seasonal, soil-based agriculture. Generally optimal growth conditions can be maintained at all times, thereby shortening the growing period from germination to maturity. Space efficiency can be maximized by rearranging the hydroponically grown plants, whose root structures are not permanently embedded in a stationary solid support. Furthermore, because hydroponic farming is generally effected in sheltered environments, e.g., greenhouses, farming is continuous throughout the year.
The recognized advantages of hydroponics must, however, be weighed against the costs of hydroponic farming, particularly initial capital costs, but also the cost of energy needed to operate a hydroponic system, the cost of nutrients which must all be supplied artificially, and substantial labor costs. An example of labor costs in efficient hydroponic systems is the labor required to rearrange plants to maximize space efficiency as the plants mature. To the extent that these costs can be reduced, the greater is the efficiency of a hydroponic system.
Compensating for any additional cost in raising plants hydroponically is that the plants may frequently be marketed in a much fresher condition. Hydrophonic farming may be carried out during all seasons in close proximity to the place of marketing. Furthermore, the entire hydroponically grown plants, including their roots, may be transported intact to market, whereby the entire live plant, and not merely its severed members, may be sold. For plants, such as certain leafy vegetables, whose foilage tends to wilt quickly after harvest, the ability to market the growing plant contributes significantly to its shelf life and its freshness as delivered to the consumer.
Hydroponic systems require some means for supporting plants in their upright orientation during their growing cycle, and pots of various types have been used in hydroponic systems. Conventional plant pots have been utilized in hydroponic farming, but more specialized plant supporting means have also been developed. U.S. Pat. No. 4,161,844 describes a plant pot for hydroculture having a compartment that contains fertilizer for nourishing the plant during its growth cycle. U.S. Pat. No. 3,927,491 describes a plant-supporting raft which may be floated on the surface of an aqueous nutrient medium. U.S. Pat. No. 4,037,360 describes a variation of such a raft having collapsible walls which naturally enlarge the space in the raft available for foilage as the plant grows.
A plant-supporting collar should be designed to promote rapid plant growth and thereby tend to maximize efficiency of the hydroponic farming operation. The collars are generally intended to be disposable because typically the hydroponically grown plant will be marketed as a still-living plant with at least a portion of its root structure intact and with the collar still surrounding the base of its stem, and therefore, the collar should be very inexpensive.